Coupling arrangement for reciprocating piston engine

ABSTRACT

A coupling arrangement for interconnecting a piston gudgeon pin and a crankshaft journal of a reciprocating piston engine, the arrangement comprising: 
     a connecting rod having a first end pivotally connected to the crankshaft journal, 
     a connection member pivotally connectable at a first pivot point to a second end of the connecting rod and pivotally connectable to the piston gudgeon pin at a second pivot point distal from the first pivot point, and 
     rotation transfer means acting to transform a rotational movement of the first pivot point about the piston gudgeon pin into a rotatioial movement of the crankshaft journal about the crankshaft.

BACKGROUND OF THE INVENTION

The invention relates to reciprocating piston engines, and in particularto coupling arrangements for interconnecting a gudgeon pin and acrankshaft journal of such an engine. The invention is applicable toreciprocating piston combustion engines and compression engines and itwill be convenient to hereinafter describe the invention in relation tothat exemplary application, although it should be appreciated that theinvention is not limited to the application.

Conventional reciprocating piston engines are generally manufactured intwo and four stroke designs. A single piston is housed within eachcylinder, the piston being connected from a central piston gudgeon pinto a single bearing crankshaft journal by a single solid center mountedconnecting rod. After combustion has taken place in the combustionchamber of the piston, the energy derived from the expansion of thecombustible material forces the piston to travel along the length of thecylinder away from the combustion chamber. This translational movementis transferred via the connecting rod to the crankshaft journal and istransformed into a rotational movement as the crankshaft is drivenaround its longitudinal axis. As the crankshaft completes eachrevolution, the connecting rod interconnecting the crankshaft journaland the gudgeon pin forces the piston back along the length of thecylinder towards the combustion chamber, where combustion once againtakes place and the cycle is repeated.

Conventional engines of this type are arranged so that the maximumcombustive pressure within the cylinder is generated when the piston isat top dead center and the crankshaft journal is at a corresponding topcenter position, that is to say, at a position closest to the cylindercombustion chamber. The resultant effect of this arrangement is thatimmediately following ignition at or slightly after the top centerposition of the crankshaft, the downward travel of the piston in thecylinder rapidly causes the enlargement of the volume of the cylinderabove the upper surface of the piston. A rapid drop in combustionpressure is thus created and there is a corresponding rapid reduction inthe force applied to the piston, and hence to the crankshaft journal forrotation of the crankshaft.

The applicant has observed that such an arrangement inefficientlyconverts energy from the combustion of gases in the combustion chamberto a motive force for turning the crankshaft. There exists a need tocreate a more efficient reciprocating piston engine where more power canbe derived from the same amount of combustible material or,alternatively, a lesser amount of combustible material may be used toachieve the same amount of power.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a reciprocatingpiston engine which overcomes or ameliorates one or more of thedisadvantages of known reciprocating piston engines.

With this in mind, the present invention provides a coupling arrangementfor interconnecting a gudgeon pin and a crankshaft journal of areciprocating piston engine, the arrangement comprising:

a connecting rod having a first end pivotally connected to thecrankshaft journal,

a connection member pivotally connectable at a first pivot point to asecond end of the connecting rod, and pivotally connectable to thegudgeon pin at a second pivot point distal from the first pivot point,and

rotation transfer means acting to transform a rotational movement of thefirst pivot point about the gudgeon pin into a rotational movement ofthe crankshaft journal about the crankshaft.

In an engine having these features, the point of attachment of theconnecting rod is separated from the gudgeon pin by a connection memberpivotally attached between the connecting rod and the gudgeon pin. Withsuch an arrangement, it is possible to create a reciprocating pistonengine in which the crankshaft journal need no longer be at a top centerposition when the piston is at its top dead center position. Thecrankshaft journal is able to be located at a position intermediate thetop center position and a bottom center position so that, at shortlyafter combustion—when the combustion chamber is at its maximum pressureand the corresponding maximum force is applied to the piston—a greatertorque is able to be applied to the crankshaft journal than is possiblewith conventional reciprocating piston engines. By maintaining orreducing the cylinder volume in the combustion chamber after thecrankshaft journal turns past its top center position, the maximumavailable force in the engine is able to be applied to the crankshaftjournal at an optimum position during its rotational cycle.

This and other advantages and features of the invention will be betterappreciated from the following description which refers in more detailto the various features of the coupling arrangement of the presentinvention. To facilitate an understanding of the invention, reference ismade in description to the accompanying drawings where the couplingarrangement is illustrated in preferred embodiments. It is to beunderstood, however, that the coupling arrangement of the presentinvention is not limited to the embodiments illustrated in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic front view of a reciprocating piston engineincluding a first embodiment of a coupling arrangement according to thepresent invention;

FIG. 2 is a side view of the reciprocating piston engine of FIG. 1;

FIG. 3 is a front view of a reciprocating piston engine including asecond embodiment of a coupling arrangement according to the presentinvention;

FIG. 4 is a side view of the reciprocating piston engine of FIG. 3;

FIG. 5 is a side view of a third embodiment of a coupling arrangementaccording to the present invention; and

FIGS. 6 to 12 are side views of the coupling arrangement of FIG. 5 invarious angular positions during operation.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, there is shown generally a single piston withina reciprocating piston engine. The piston I is located within a cylinder2. The engine also includes a crankshaft 3 and a crankshaft journal 4maintained at a position radially displaced from the longitudinal axisof the crankshaft 3 by crankshaft rods 5. In the position shown in FIG.1, the crankshaft journal is at a top center position. The piston 1incorporates a piston gudgeon pin 6.

A coupling arrangement is provided for interconnecting the pistongudgeon pin 6 and the crankshaft journal 4 of the engine. This couplingarrangement comprises a connecting rod including two connecting rodhalves 7 and 8 each of which has a first end pivotally connectable tothe crankshaft journal 4 via a split bearing arrangement.

A connection member 9. in this case a cam disc, is pivotally connectableat a first pivot point (the center of the cam disc 9, as can be bestseen in FIG. 2) to a second end of the connecting rod 7, 8. The cam disc9 is also pivotally connectable to the gudgeon pin 6 at a second pivotpoint distal from the first pivot point, that is to say, that the pointat which the cam disc 9 is attached to the piston gudgeon pin 6 is offcenter from the center of the cam disc 9.

The coupling arrangement also includes rotation transfer mechanismacting to transform a rotational movement of the first pivot point aboutthe gudgeon pin 6 into a rotational movement of the crankshaft journal 4about the crankshaft 3. In the example illustrated in FIGS. 1 and 2, therotation transfer mechanism includes a gear train or like mechanisminterconnecting the first pivot point (the center of the cam disc 9) andthe crankshaft journal. The gear train includes a crankshaft gear 10centrally located and fixedly held about the crankshaft journal 4 sothat it is unable to independently rotate around the longitudinal axisof the crankshaft journal 4. The rotation transfer mechanism alsoincludes a secondary gear 11 mounted to at least one of the connectingrod halves 7, 8 by a secondary gear retaining pin 12 and about which thesecondary gear is able to rotate. Similarly, an idler gear 13 is mountedto at least one of the connecting rods 7, 8 via an idler gear retainingpin 14. A cam disc gear 15 is fixedly attached to the cam disc 9. Whenmounted in position, the crankshaft gear 10 is positioned so as tointeract and mesh with the secondary gear 11, which in turn interactsand meshes with the idler gear 13. The idler gear 13 interacts with andmeshes with the cam disc gear 15. According to such an arrangement, asthe piston 1 is driven up and down the bore of the cylinder 2, the camdisc 9 will be caused to rotate around the piston gudgeon pin 6. As thecenter of the cam disc 9 rotates around the gudgeon pin 6. the geartrain 15, 13, 11 and 10 ensures that the rotational movement of the camdisc center is transferred to the crankshaft journal with the resultthat the crankshaft journal is driven in a rotational movement about thecrankshaft 3. Moreover, these two rotational movements are synchronizedso that the angular displacement of the first pivot point, or center ofthe cam disc 9, and of the crankshaft journal is the same, each startingand completing a 360° revolution at the same time as the other.

The cam disc 9 and the cam disc gear 15 are held in position by theconnecting rod halves 7, 8 to allow the piston gudgeon pin 6 to passfrom one side of the piston 1 through the cam disc 9 and cam disc gear15 to the other side of the piston 1, securely connecting the piston 1to the crankshaft journal 4 by means of the above described couplingarrangement. As the cam disc gear 15 and the cam disc 9 rotate, thepiston gudgeon pin 6 is forced to rotate also. As the gudgeon pin 20rotates it can be seen from FIG. 2 that the distance between thecrankshaft journal 4 and the piston 1 will be cyclically lengthened andthen shortened. as the center of the cam disc 9 rotates around the offcenter mounting position of the cam disc 9 on the gudgeon pin 6.

FIGS. 3 and 4 show an alternative embodiment of the couplingarrangement, in which the rotation transfer mechanism further includes achain or like mechanism interconnecting two or more gears in the geartrain. In this embodiment, the crankshaft journal gear 10, and the camdisc 9 and associated cam disc gear 15, have been retained and areconnected respectively to the piston gudgeon pin 6 and the crankshaftjournal 4 in the manner previously described. However, in thisembodiment, the cam disc gear 15 and the crankshaft journal disc 10 areinterconnected by a chain 16. According to this arrangement, thedirection of rotation of the cam disc gear 15 and of the crankshaftjournal disc 10 will be the same, where as these two gears were causedto rotate in opposite directions in the arrangement shown in FIGS. 1 and2.

It is to be appreciated that whereas the arrangements in FIGS. 1 to 4show the interconnection of various gears and chains, a variety of likemechanisms may be used in the context of the present invention. Forexample, coupling arrangements using pulleys and belts and other devicesfor the transfer of rotational movement may easily be envisaged by askilled worker in this field.

Either of the two embodiments shown in FIGS. 1 and 2, and FIGS. 3 and 4,enable the setting of the angular position of the first pivot point (orcenter of the cam disc 9) with respect to the gudgeon pin 6, as well asthe angular position of the crankshaft journal 4 with respect to thecrankshaft, so that, unlike conventional reciprocating piston engines,the top dead center position of the piston 1 need not necessarilyrequire that the crankshaft journal 4 be located in its top center oruppermost position. An example of this will now be described withreference to FIG. 5, which shows schematically the crankshaft journal 4,crankshaft 3 and gudgeon pin 6. A connecting rod 20 is pivotallyconnected at a first end to the crankshaft journal 4. A connectionmember 21 is pivotally connected at a first pivot point 22 to a secondend of a connecting rod 20. The connection member 21 is also pivotallyconnected to the gudgeon pin 6 at a second pivot point 23 distal fromthe first pivot point 22. It will be noted that in this case, theconnection member 21 is not in the form of a disc, and that the rotationtransfer mechanism is formed by two intermeshing gears only, referenced24 and 25, which are respectively fixed or otherwise mounted to theconnection member 21 around the first pivoy point 22 and fixed aroundthe crankshaft journal 4. From this diagram, it can be seen that whilstthe angular position of the first pivot point 22 with respect to thegudgeon pin is approximately 180° with respect to a reference axis 30,the angular position of the crankshaft journal 4 with respect to thecrankshaft 3 is approximately 270° with respect to that same referenceaxis. As ignition occurs, the piston 1 is forced down in the cylinder 2,and force is transmitted from the gudgeon pin through the connectingmember 21 and the connecting rod 20 to the crankshaft journal 4. As thecrankshaft journal 4 is no longer at its top center or uppermostposition when piston 1 is at top dead center, but, as shown, is locatedlaterally from the crankshaft 3 at a horizontal distance “h”. The forceapplied to the crankshaft journal 4 at the instant just after ignitionresults in a substantially increased torque being applied to thecrankshaft journal 4. Consequently, the engine is able to develop morepower than conventional reciprocating engines. As the crankshaft journal4 is driven anti-clockwise (as shown in FIG. 5) around the longitudinalaxis of the crankshaft 3, the gear 25 is caused to rotate in thedirection shown by the arrow referenced 32. This causes a correspondingrotation of the gear 24 in the direction shown by the arrow 31. Thisrotation causes the first pivot point 22 of the connection member 21 tobe driven in a clockwise direction around the gudgeon pin 6.

The various exemplary embodiments of the rotation transfer mechanismshown in the drawings act to maintain the angular position of the firstpivot point with respect to the gudgeon pin, and the angular position ofthe crankshaft journal with respect to the crankshaft, at a fixedseparation during operation of the engine. By way of example, in FIG. 5the angular position of the first pivot point 22 with respect to thegudgeon pin 6 is approximately 180° with respect to the reference axis30. The angular position of the crankshaft journal 4 with respect to thecrankshaft is approximately 270° with respect to that same referenceaxis. The separation between these two angular positions is thereforeapproximately 90°. As the gears 24 and 25 mesh with each other duringoperation of the engine, both the crankshaft journal 4 and the firstpivot point 22 rotate synchronously, respectively about the longitudinalaxis of the crankshaft 3 and the piston gudgeon pin 6, so that rotationstarts and stops at the same time and that after each revolution theangular position of the first pivot point and of the crankshaft journalwill be as shown in FIG. 5.

FIGS. 6 to 12 show the relative angular positions of the couplingarrangement of FIG. 5 through a complete revolution of the first pivotpoint 22 about the piston gudgeon pin 6. FIGS. 6 to 9 show the couplingarrangement at 60 degree intervals, whilst the angular spacing betweenrepresentations of FIGS. 9 to 12 is 30 degrees.

Returning once again to FIG. 2, it can be seen that the rotationtransfer mechanism according to this embodiment enables the relativeangular positions of the first pivot point and the crankshaft journalduring operation of the engine to be adjusted. In this embodiment, toset the relative angular positions just mentioned, one of the connectingrod halves 7 or 8 may be removed and one or both of the secondary gear11 or idler gear 13 removed so that, temporarily, rotational movement isnot transferred from the cam disc 9 to the crankshaft journal disc 10.The angular position of the center of the cam disc 9 with respect to thegudgeon pin 6 may then be set by rotating the cam disc gear 15 to thedesired position. Similarly, the crankshaft journal 4 may be rotatedaround the longitudinal axis of the crankshaft 3 to achieve a desiredangular position. Next, the piston 1 may be displaced up or down thecylinder 2 so that the secondary or idler gear removed may be reinsertedand the connecting rod halves 7, 8 reattached to both the crankshaftjournal and the cam disc. In this way, both the angular position of thefirst pivot point with respect to the gudgeon pin, and the angularposition of the crankshaft journal with respect to the crankshaft, maybe independently set at any desired value.

It has been found experimentally that the present invention provides notonly the advantage of developing more torque within the engine at themoment of combustion or maximum compression, but also provides severalother advantages depending upon the relative angular positions of thefirst pivot point and the crankshaft journal during operation of theengine. For example, it is possible to vary the length of the pistontravel within the cylinder by changing the relative angular positions ofthe first pivot point and the crankshaft journal.

It is also possible to vary the speed of travel of the piston within thecylinder at various stages of the cycle of operation of the engine. Forexample, it is possible to choose relative angular positions of thefirst pivot point and the crankshaft journal so that the speed of travelof the piston in the proximity of its bottom dead center position isreduced. In this configuration, the piston spends a large proportion ofits time in the bottom of the cylinder, thus allowing an increasedamount of time for the exhaust of waste combustion gases (when thecoupling arrangement of the present invention is used in a reciprocatingpiston combustion engine).

The rotation transfer mechanism may also enable the adjustment of therelative lengths of the distance from the second to the first pivotpoints of the connection member and the distance from the crankshaftjournal to the crankshaft. For example, the cam disc of FIGS. 1 to 4 maybe provided with one or more locations at which the disc may be attachedto the gudgeon pin 6. Each of these locations may be at varyingdistances from the center of the cam disc 9. Some of these locations maybe at a greater distance from the center of the cam disc 9 than thedistance from the crankshaft journal to the crankshaft, whilst othersmay be at a smaller distance. If a relatively large distance is selectedbetween the center of the cam disc 9 and the gudgeon pin 6, a givenangular displacement of the cam disc 9 will result in a relatively largetravel of the piston within the cylinder. Conversely, the selection of arelatively small distance between the center of the cam disc 9 and thegudgeon pin 6 will mean that for a relatively small distance travelledby the piston in the cylinder 2, a significant angular displacement ofthe cam disc 9 will take place, resulting in a corresponding significantrotation of the crankshaft journal around the crankshaft. It will beappreciated that a variety of configurations of this nature may bedesired depending upon the characteristics of the engine and itsperformance that may be sought.

Those skilled in the art will appreciate that there may be variationsand modifications of the connection arrangement described herein whichare within the scope of the present invention.

What is claimed is:
 1. A coupling arrangement for interconnecting apiston gudgeon pin and a crankshaft journal of a reciprocating pistonengine, the arrangement comprising: a connecting rod having a first endpivotally connectable to the crankshaft journal, a connection memberpivotally connectable at a first pivot point to a second end of theconnecting rod, and pivotally connectable to the piston gudgeon pin at asecond pivot point distal from the first pivot point, and rotationtransfer means acting to transform a rotational movement of the firstpivot point about the piston gudgeon pin into a rotational movement ofthe crankshaft journal about the crankshaft.
 2. A coupling arrangementaccording to claim 1, wherein the rotation transfer means are adjustableto set the relative angular positions of the first pivot point and thecrankshaft journal.
 3. A coupling arrangement according to claim 1,wherein the rotation transfer means are adjustable to set the relativelengths of the distance from the second pivot point and the first pivotpoint and the distance from the crankshaft journal to the crankshaft. 4.A coupling arrangement according to claim 1, wherein the rotationtransfer means includes a gear train interconnecting the first pivotpoint and the crankshaft journal.
 5. A coupling arrangement according toclaim 4, wherein the rotation transfer means further includes a chaininterconnecting two or more gears in the gear train.
 6. A couplingarrangement according to claim 7, wherein at least a portion of the geartrain is mounted to or maintained in position by the connecting rod. 7.A coupling arrangement according to claim 1, wherein the gear trainincludes a first gear fixedly attached to the crankshaft journal.
 8. Acoupling arrangement according to claim 7, wherein the gear trainincludes a second gear fixedly attached to the connecting member.
 9. Acombustion engine including a piston gudgeon pin and a crankshaftjournal interconnected by a coupling arrangement according to claim 1.10. A compression engine including a coupling arrangement according toclaim 1.